Combine peanut butter cups and candy coating in a microwave safe bowl. Microwave for 20 seconds, stir and continue to microwave in 20 second intervals until completely melted.
Pour chocolate over popcorn and stir until chocolate evenly covers popcorn. Stir Reese's Pieces into the popcorn and spread onto a baking sheet to cool and harden. Once coating is set, break into bite-sized pieces if needed.